Sealing-in apparatus



oct. 3,i 1944.

- A. J. WHITE 'fsEALING-IN APPARATUS original Fiied Nov. 27, 1937 mg. yz;

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`Patented- Oct. 3, 1944 UNITED STATESl PATENT OFFICE SEALING -lN APPARATUS Arthur J. White, Cleveland Heights, Ohio, assignor toGeneral Electric Company, a corporation `oi' New York original application November 27, 1937, serial Divided and thisv application March 22, 1944, Serial No. 527,542 v comme- (ci. 49 53) My invention relates to apparatus for sealing together the ends of tubular glass members, and more particularly to apparatus for sealing glass stems in the bulbs or envelopes of electric lamps or similar devices. This application is a division of my application Serial No. 176,910, filed November 27, 1937.l

Stems for electric lamps and similar devices j generally comprise a glass stem tube having one end fused around a portion of one or more leadin'wires extending through the tube, the other end of said tube being' dared or flanged outward. The stem is sealed in a lbulb or envelope by inserting it therein and then applying gas names to fuse the open end or neck portion of said bulb or envelope and the ange. on said stem viate the above-mentioned disadvantages and 9 will seal a stem in an envelope without distortion of the portion of the envelope adjacent to the sealed joint. Another object is to provide apparatus by which the stem is quickly and eflfciently sealed`in the envelope to produce a hermetical seal free' from cracks. Other objects and advantages of my invention `will appear from the following description and from the accompanying drawing. In the drawing, Fig. 1 is an elevation, mostly 1n section, of a tubular electric discharge lamp and a fportion of an apparatus for sealing stems in the ends of the tubular envelope of the lamp 1n accordance with iny invention, and Fig. 2 is an elevation, mostlyin section, showing one end of the lamp with a base attached thereto.

According to my invention, the method of sealing with my apparatus consists generally in placing a stem with its flanged end resting on a disc or ring of a material which is capable of being heated by induction and will not adhere to the fused glass, such as carbon. The envelope is then placed over the st em with its open end or neck portion resting on the flange or adjacent thereto. The said disc or ring' is then heated to a high degree by induction to cause the adjacent ends of the stem and envelope to be fused and sealed together by conduction and radiation of heat from the said disc or ring. Pressuremay be applied at the opposite end of the envelope, if desired, to press the fused ends of the envelope and stem thereagainst.

Referring to Fig. 1, the lamp illustrated therein in process of assembly comprises a tubular glass envelope I0 having a stem Il at its upper end (shown as already sealed in), and` another stem I2 at its lower end about to be sealed in. The said stem I2 is of the so-called tipless variety and comprises a glass sternl tube I3 and an exhaust tube I4 which are 'fused at their upper ends to form a mass of glass I5 enclosing portions of lead-in Wires lli-I6, there being an axial vopening I1 through the said' massof glass formed by blowing through the said-exhaust tube I4. An electrode I8, consisting preferably of a coiled-coil of tungsten wire coated with an electron emissive material such asbarium and/or strontium oxide, is secured at its ends to the inner ends of the lead-in wires lli-I6. vIt is very desirable that the stems be as short as possible in order that the electrodes I8-I8 may be close to the ends of the envelope III. Therefore, in making the stem I2 it is held in an ulpright posltion and the upper ends of the steml tube I3 and exhaust tube I4 are heated to fusion by gas ames, causing them to collapse and flow down lalong the lead-in wires I6- I6. to form the solid mass of glass I5. While the glass mass I5 is still plastic, air pressure is 'applied to the exhaust tube I4 to blow the opening l1, there being-no compression or pressing of the glass mass I5 by a pair ofjaws at any time as is the usual present practice. Air is also blown into the space between the exhaust tube I4 andl stem tube I3 `vto round out the joint therebetween,

thereby eliminating sharp corners which may lead to cracks. During the flowing of the glass made in the same manner except, of course, that the exhaust tube I4 is omitted. This method of making the stems is described and claimed in my Patent No. 2,128,173. Of course, vstems made according to standard practice may be used if desired.

For sealing in the stem l2, I have illustrated in Fig. 1 an apparatus comprising asupportrodor block is of refractory insulating material, such as sillimanite, having a disc-or ring 20 of material which is capable of being heated by induction and will not adhere to glass, preferably carbon, placed on its upper end. The stem I2 is placed with its flanged end 2| resting on the disc 20 in abutting relation therewith, the exhaust tube I4 and lead-in wires Iii- I6 extending into an axial opening 22 in the support rod I9. The envelope i is then clamped in the Jaws of a holder 3l and it is lowered until the reduced open end or neckportion 23 thereof rests on the flange 2|. A coil 24, which is connected to a suitable source 32 of high frequency current, is then slowly raised by a lever.33, for example, so as to surround the disc 2li,` thereby heating the said disc by induction to a very high degree and causing the envelope neck 23 and ange 2l to be fused and sealed together. Pressure is preferably applied to the envelope I0 during the sealing operation, for example, by a suitable weight 25. By this method of sealing the neck 23 of the envelope is not distorted, no r is the shoulder 28 distorted, nor is any portion of the short stem I2 distorted. The envelope l0 and stem l2 are permitted to remain on the disc 20 for a short period after the current flow to coil 24 has been interrupted so that the sealed joint is annealed.

By making the flange 2l large enough to extend a short distance beyond the neck 23 of the bulb, as shown in Fig. 1, a small bead 21 may be formed at the sealed joint which may be desirable for preventing the base from being pulled oif the envelope. In Fig. 2,-I have illustrated one of pins 30-30 to which are connected the leadin wires iS-IS.

What I claim as new and desire to secure by Letters Patent of the United States is:

1; In apparatus for sealingv a glass bulb-to a stem having a flare,v the combination of a carbon ring on which the flare may be placed, a holder for said bulb above and in register with said carbon ring, a refractory holder for said carbon ring, a metal coil normally out of inductive relation to said carbon ring, a source of high frequency power connected to said coil, and means for bringing said coil and ring into inductive relationship to heat said ring sufficiently to effect a seal between the glass bulb and the'ilare of the stem.

2. In apparatus for sealing a glass bulb to a stem having a. flare, the combination of a ring on which the flare may be placed, said ring being made. of a material which is capable of being heated by induction and to which the fused glass will not permanently adhere, a holder for said bulb above and in register with said ring, Aa refractory holder for said ring, a metal coil normally out of inductive relation rto said ring, a source of high frequency power connected to said coil, and means for bringing said coil and ring into inductive relationship to heat said ring sufficiently to effect a seal between the glass bulb and the flare of the stem.

3, Apparatus for sealing a plurality of vitreous bodies together comprising a heating element vof material to which the fused vitreous bodies will not permanently adhere, said element being arranged to engage and support one of the vitreous bodies at the area where it is to be sealed, gripping means for holding a second vitreous body against the first-mentioned body, means for raising the temperatureof the heating element so that heat is conducted to the vitreous bodies in sufficient quantity to vcause the adiacent portions thereof to be fused together, and means for moving said vitreous bodies toward each other to effect a more positive seal therebetween.

4. In apparatus for sealing a glass bulb to a stem having a flare, the combination of a carbon ring on which the flare may be placed, a

holder for said bulb above and in register with said carbon ring, a refractory holder for said carboni ring, a metal coil normally out of induc tive relation to said carbon ring, and a source of high frequency power connected to said coil, said coil being constructed and arranged to be moved into a position surrounding said ring to heat the ring sufficiently to eect a seal between the glass bulb and the flare of the stem.

5. In apparatus for sealing a vglass bulb to a stern having-a are, the combination of a carbon ring on which the nare may be placed, a holder for said bulb above and in register with said carbon ring, a refractory holder for said carbon ring, a metal coil normally out of inductive relation to said carbon ring, and, a source of high frequency power connected to said coil, said coil and ring being arranged to be brought into inductive relationship to heat said ring sufilciently to effect a seal between the glass'bulb and the flare of the stem.

6. Apparatus for sealing a glass bulb to a stem having a flare comprising a heating element of material to which the fused glass will not permanently adhere, said element being arranged to engage and support the stem at its periphery, gripping means for holding the bulb with its end engaging the flare of said stem, means for raising the temperature of the heating element so that heat is conducted to the stem and bulb in sufficient quantity to cause the adjacent peripheral portions thereof to be fused together, and

means for exerting pressure longitudinally of the y bulb to cause the fused portions of the bulb and 

